Dry developer for an electrostatic image developing apparatus

ABSTRACT

The present invention relates to a dry developer apparatus for forming a magnetic brush in electrostatic image development, wherein the developer composed of a magnetic carrier and toner magnetically adheres to a rotary roller having a specific magnetic pole. The magnetic brush is formed between the rotary roller and an opposed plate of different magnetic polarity which is mounted in parallel spaced relationship to the rotary roller by a control permanent magnet mounted in parallel spaced relationship to the roller. Rotation of the permanent magnet so that a magnetic polarity opposite to that of the roller causes the developer to be attracted to the roller surface.

United States Patent Ogawa Mar. 14, 1972 [54] DRY DEVELOPER FOR AN 3,572,288 3/1971 Turner ..1 18/637 ELECTROSTATIC IMAGE 3,133,833 5/1964 Giaimo,Jr. DEVELOPING APPARATUS 2,892,446 6/1959 Olden 2,930,351 3/1960 Giaimo, Jr. ..1 18/637 [72] Inventor: Masaya Ogawa, Osaka, Japan Primary Examiner-Mervin Stein [73] Assignee: Minolta Camera Kabushiki Kaisha, Osaka, Assistant Examine, Leo Miiistein Japan Attorney-Watson, Cole, Grindle & Watson [22] Filed: July 7, 1970 ABSTRACT Appl' The present invention relates to a dry developer apparatus for forming a magnetic brush in electrostatic image development, [30] Foreign Application Priority Data wherein the developer composed of a magnetic carrier and toner magnetically adheres to a rotary roller having a specific July 8, 1969 Japan ..44/53984 magnetic p The g i brush is formed between the July 1969 Japan "44/56197 tary roller and an opposed plate of different magnetic polarity July 10, 1969 Japan ..44/653l0 which is mounted in paiaiiei spaced relationship to the rotary roller by a control permanent magnet mounted in parallel [52] US. Cl ..l18/637, l 17/ 17.5; 209/219 spaced relationship to the roller, Rotation of the permanent [51] lnt.Cl. ..G03g 13/00 magnet so that a magnetic polarity opposite to that of the [58] Field of Search ..118/637; 117/ 17.5; 209/219 roller causes the developer to be attracted to the roller surface.

[56] References Cited 4 Claims, 5 Drawing Figures UNITED STATES PATENTS 3,058,444 10/1962 Sugannan et al. ..118/637 Patented March 14, 1972 2 Sheets-Sheet 1 INVENTOR ATTORNEY Patented March 14, 1972 2 Sheets-Sheet 2':

FIG.5

" INVENTOR 'Mn ATTORNEY DRY DEVELOPER FOR AN ELECTROSTATIC IMAGE DEVELOPING APPARATUS BACKGROUND OF THE INVENTION In a dry developer apparatus for forming a magnetic brush, when development is not desired it is necessary to stop the formation of a magnetic brush to prevent the developer from scattering and adhering to a developing member, thereby facilitating the cleaning of the developing apparatus.

Known dry developing apparatus are generally of two types. The first type makes use of an electromagnet to magnetize or demagnetize a developing member by turning the exciting current ON or off. The second type makes use of a permanent magnet and when the development is not desired an opposed plate is retracted from a rotary roller developing member, or the magnetic polarity of opposed plate is reversed to the opposite polarity, or an insulator is provided on the back of the opposed plate. In the former type, when development is not to take place it is possible to prevent the developer from adhering to the rotary roller, however, when the development is to be operative the exciting current must be high so that the electric power required is increased and it is difficult to supply it from an ordinary electric power source such as is normally available in an office. In the latter type, the electric power required for the exciting current is not increased, however, in general the opposed plate is required to be of a large size in order to form a good magnetic brush, so that when the plate is moved or rotated a large space is required on the upper side of the developing apparatus and the size of the whole apparatus is increased.

SUMMARY OF THE INVENTION In the present invention, in order to solve the problems mentioned above, the rotary roller and the opposed plate are made of magnetic materials, and between both ends thereof permanent magnets are provided so as to polarize the rotary roller and opposed plate with a different polarity by a magnetic flux therebetween. To control the formation and deformation of the magnetic brush by the presence or absence of magnetic flux, control permanent magnetic pieces are mounted in parallel spaced relationship with the roller outside the developer reservoir, and the magnetic pole of the control permanent magnetic pieces facing the rotary roller can be rotated so as to be of the same polarity as that of the rotary roller or of opposite polarity from that of the roller.

The primary object of the present invention is to provide a small-sized dry developing apparatus in which the formation and deformation of a magnetic brush on a rotary roller may be controlled in accordance with the development and nondevelopment of electrostatic images.

The second object of the present invention is to provide a dry developing apparatus which prevents the developer from scattering during non development of the electrostatic image so as to facilitate cleaning of the developing apparatus, especially near the bearings of the rotary roller.

The third object of the present invention is to provide a dry developing apparatus which enhances the magnetic brush formed between the rotary roller and the opposed plate and prevents the developer from entering the bearings of the apparatus.

The fourth object of the present invention is to provide a dry developing apparatus in which the extent of the magnetic brush formed between the rotary roller and the opposed plate may be controlled in accordance with a desirable developing width in the axial direction of the rotary roller.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an embodiment of a dry developing apparatus for electrostatic images in accordance with present invention.

FIG. 2 is a sectional side view taken at the central portion of the rotary roller during operative development in the embodiment shown in FIG. I.

FIG. 3 is a sectional side view as in FIG. 2 wherein the development is not operative.

FIG. 4 is a sectional side view near the end portion of the rotary roller showing operative development in the embodiment of FIG. 1.

FIG. 5 is a perspective view of another embodiment of a dry developing apparatus for electrostatic images in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIGS. from 1 to 4, an embodiment of a dry developing apparatus for electrostatic images in accordance with the present invention will be described hereinafter.

Rotary roller 1 composed of a magnetic material is supported on both sides thereof rotatably by bearings 3, 3' also composed of a magnetic material and mounted on both side plates of developer reservoir 2, and shaft la of one end thereof projects out of bearing 3 and pulley 6 is fixed thereto.

Both side portions Ic near both bearings 3, 3' of rotary roller 1 are formed respectively into a smooth tubular surface having a small coefiicient of friction (by electrolytic polishing or buff polishing) and the central portion lb thereof is formed into a roughened surface having a large coefficient of friction (by a sand-blast process, a chemical etching process, or a knurling working process).

On the upper faces of both bearings 3, 3' two permanent magnets 5, 5 of the same shape are fixedly mounted, and on magnets 5, 5' opposed plate 4 composed of a magnetic material is fixedly mounted so as to be parallel with rotary roller 1. The polarities of both permanent magnets 5, 5' are such that the polarities of their respective lower faces coincide with each other, that is, in FIG. 1 the lower faces of both permanent magnet 5, 5' are of S polarity and the upper faces are of N polarity. Therefore, rotary roller I is magnetized with an S polarity and the opposite face of opposed plate 4 is magnetized with an N polarity.

Pully 6 is coupled with pulley 7a of prime mover 7 by belt 8 and the rotary roller rotates in the direction shown by arrows in FIGS. from 2 to 4, namely, counterclockwise. Pulsator 9 is rotatably supported by both side plates of reservoir 2 parallel and lower with respect to rotary roller 1 and is provided with blades 9b. On shaft extending thereof outside of the side plate pulley 10 is fixed and between pulley l0 and driving pulley 11a of prime mover 11 belt 12 is provided and thereby pulsator 9 is rotated in the opposite direction to rotary roller 1.

Between bearings l6, 16' formed on the outer wall of reservoir 2 on the same side as said pulsator 9, one long control permanent magnet 15 is mounted to shaft 15a so as to be parallel with rotary roller 1 and rotated manually by knobs I7, 17' fixed to both ends of shaft 15a. Control permanent magnet 15 is composed of a long rectangularly shaped tubular body, and one face of the tube thereof parallel with rotary roller 1 is of one polarity, for example, 8 polarity and the opposite side thereof is of the opposite polarity, namely, N polarity.

In developer reservoir 2 developer 18 composed of a toner and magnetic carrier is put nearly half full to bury pulsator 9 and from one-third to one-half portion of the lower side of rotary roller 1 is in contact with developer 18.

Photosensitive paper or photosensitive plate 13 on which an electrostatic latent image is formed is carried in the direction shown by arrow 14 in FIGS. 1 and 2 by means of a carrier roller not shown in the drawings, and passes between the upper edge of reservoir 2 and opposed plate 4.

Rotary roller 1 and pulsator 9 are rotated by prime movers 7, I] through belts 8, 12 in opposite directions to each other as shown by the arrows in FIGS. from 2 to 4. Reference numeral 19 denotes a cleaning spatula for removing developer 18 adhering to rotary roller I.

Now, when photosensitive paper 13 is not carried to the developing apparatus and the development thereof is not operative. as shown in FIG. 3 by control permanent magnet being rotated so that an S pole faces the S pole of rotary roller 1. Even though developer 18 is forced up along face 1b of rotary roller 1 on account of the rotation of rotary roller 1 and pulsator 9, magnetic repulsion between rotary roller 1 and control permanent magnet 15, so that a magnetic brush is not formed and accordingly almost all of developer 18 is dropped by gravity and the developer is not scattered and consequently the surface of the roller is not contaminated.

Next, when photosensitive paper 13 is carried to be developed, control permanent magnet 15 is reversed manually by knob 17 as shown in FIG. 2. And thus, the N pole of control permanent magnet 15 faces rotary roller 1 magnetized to have an S polarity, and onto roughened surface 1b on the central portion of rotary roller 1 a large quantity of developer is formed on account of the rotation of rotary roller 1 and pulsator 9. A magnetic brush is formed by the magnetic flux which is aided by the rotation of rotary roller 1 between rotary roller 1 and opposed plate 4. The magnetic brush is applied to an electrostatic image on photosensitive paper 13, so that a large quantity of the developer is supplied uniformly to the photosensitive paper and the developer adheres where an electrostatic charge is located. In this case, magnetic flux between control permanent magnet 15 and rotary roller 1 enhances the magnetic brush formed between rotary roller 1 and opposed plate 4.

On the contrary, on smooth portion 1c of both ends of rotary roller the developer slips and drops without adhering upon the rotation of rotary roller 1, and the magnetic brush is not formed on smooth portion 10.

Therefore, even though photosensitive paper 13 passes by both ends of rotary roller 1 developer is not brushed onto the opposing portion thereof. Further because both smooth portions are in contact with bearings 3, 3' of rotary roller 1 it is possible to prevent the developer from going into bearings 3, 3' and from damaging the roller shaft or the inside of bearings by abrasive actionv Besides, after a duplication is finished, when the duplicator is inoperative the cleaning of the outside and inside of developer reservoir 2 is facilitated by reversing control permanent magnet 15 as shown in FIG. 3.

In another embodiment shown in FIG. 5, one long control permanent magnet is divided into control magnet pieces 15 to 15 which are mounted in a line on common shaft 20 supported by bearings 21, 21 in the outer side wall of developer reservoir 2 so as to rotate respectively relative to shaft 20, and equipped to be reversible so that one magnetic pole S or the other magnetic pole N may face rotary roller 1 by means of a spring or a click stop mechanism not shown in the drawings.

And, magnetic pieces from 15 to 15,, corresponding to the width A of photosensitive paper 13 to be developed face rotary roller 1 to form magnetic flux therebetween, and magnetic pieces 15,, 15 and 15 15 on both sides corresponding to portions B, B where photosensitive paper 13 does not pass by and are rotated to present the same polarity as the end positions of the roller, so that it is possible to prevent the developer on both portions 13, B from scattering and entering bearings 3, 3, and the formation of a magnetic brush can be restricted only on a desired portion of rotary roller 1 and opposed plate 4. In this embodiment, as described above the formation of magnetic brush can be controlled by the control electromagnetic pieces, therefore, as shown by the aforementioned embodiment rotary roller 1 is not required to have a rough center portion and smooth side portions, although such separate portions can be effected as well.

Additionally the formation of other parts in this embodiment is equivalent to that of the aforementioned embodiment and the same parts have been designated by the same reference numerals.

I claim:

1. A dry developing apparatus for electrostatic images, comprising: a developer composed of a magnetic carrier and toner, a reservoir for retaining said developer, a magnetic roller supported rotatably on said reservoir, a stationary magnetic plate mounted in parallel opposed spaced relationship to said roller, magnets interposed between the ends of said rotary roller and said opposed plate to magnetize said roller and said plate to opposite polarities, a control permanent magnet rotatably to the outer side wall of said reservoir and parallel to said rotary roller, said control permanent magnet controlling the attraction of said developer onto said roller wherein developer is formed on said roller with said control magnet positioned to have a different polarity than said roller and repulsing said developer from said roller with said permanent magnet positioned to have the same polarity as said roller.

2. A dry developing apparatus as in claim 1, wherein said rotary roller has a tubular surface with smooth surface portions at each end adjacent said reservoir and a roughened surface between said end portions for retaining developer thereon.

3. A dry developing apparatus as in claim 1, wherein said developer reservoir includes a pulsator mounted by a shaft parallel to said rotary roller and at a lower elevation within said reservoir to rotate in the opposite direction to said rotary roller.

4. A dry developing apparatus, comprising: a developer of a magnetic carrier and toner, a reservoir for retaining said developer, a magnetic roller supported rotatably on said reservoir, a stationary magnetic plate mounted in parallel opposed spaced relationship to said roller, magnets interposed between said rotary roller and said opposed plate to magnetize each member to a different polarity respectively, a shaft mounted parallel to said rotary roller on the outer side wall of said reservoir, a plurality of control permanent magnetic elements each mounted rotatably on said shaft for controlling the formation of a magnetic brush on said rotary roller whereby said developer is attracted to or repulsed from desired portions of said magnetic roller with said permanent magnetic elements selectively positioned to have the same or different polarity as said magnetic roller. 

1. A dry developing apparatus for electrostatic images, comprising: a developer composed of a magnetic carrier and toner, a reservoir for retaining said developer, a magnetic roller supported rotatably on said reservoir, a stationary magnetic plate mounted in parallel opposed spaced relationship to said roller, magnets interposed between the ends of said rotary roller and said opposed plate to magnetize said roller and said plate to opposite polarities, a control permanent magnet mounted rotatably to the outer side wall of said reservoir and parallel to said rotary roller, said control permanent magnet controlling the attraction of said developer onto said roller wherein developer is formed on said roller with said control magnet positioned to have a different polarity than said roller and repulsing said developer from said roller with said permanent magnet positioned to have the same polarity as said roller.
 2. A dry developing apparatus as in claim 1, wherein said rotary roller has a tubular surface with smooth surface portions at each end adjacent said reservoir and a roughened surface between said end portions for retaining developer thereon.
 3. A dry developing apparatus as in claim 1, wherein said developer reservoir includes a pulsator mounted by a shaft parallel to said rotary roller and at a lower elevation within said reservoir to rotate in the opposite direction to said rotary roller.
 4. A dry developing apparatus, comprising: a developer of a magnetic carrier and toner, a reservoir for retaining said developer, a magnetic roller supported rotatably on said reservoir, a stationary magnetic plate mounted in parallel opposed spaced relationship to said roller, magnets interposed between said rotary roller and said opposed plate to magnetize each member to a different polarity respectively, a shaft mounted parallel to said rotary roller on the outer side wall of said reservoir, a plurality of control permanent magnetic elements each mounted rotatably on said shaft for controlling the formation of a magnetic brush on said rotary roller whereby said developer is attracted to or repulsed from desired portions of said magnetic roller with said permanent magnetic elements selectively positioned to have the same or different polarity as said magnetic roller. 